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The Cambridge of eighteen hundred and ninety-six: a picture of the city and its industries fifty years after its incorporation (ed. Arthur Gilman) 22 0 Browse Search
Harper's Encyclopedia of United States History (ed. Benson Lossing) 20 0 Browse Search
Cambridge sketches (ed. Estelle M. H. Merrill) 14 0 Browse Search
Knight's Mechanical Encyclopedia (ed. Knight) 13 1 Browse Search
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Browsing named entities in Knight's Mechanical Encyclopedia (ed. Knight). You can also browse the collection for Alvan Clark or search for Alvan Clark in all documents.

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Knight's Mechanical Encyclopedia (ed. Knight), A. (search)
nstruments at a very great expense. The Greenwich Observatory was erected five years later; Flamstead, under the title of Astronomer Royal, was its first superintendent. The Yale College Observatory was started in 1828, a donation made by Mr. Clark being expended in buying a telescope of Mr. Dollond of London. It has a focal length of ten feet, and five inches aperture. The Williams College Observatory was the first regularly constituted observatory in the United States, 1836. It hassual with that class of instruments. Sidereal motion is communicated to the instrument by clock-work. Its objectglass is 25 inches in diameter. The new refracting instrument for the Naval Observatory of Washington, D. C., is being made by Alvan Clark, of Cambridgeport, Mass., and will probably be completed during the present year (1873). Its object-glass is complete, and has a diameter of 27 inches. It is the largest of its class, and great hopes are reasonably entertained of its performan
Knight's Mechanical Encyclopedia (ed. Knight), T. (search)
mpracticable. The improvement in this respect is in a large degree due to the exertions of Mr. Alvan Clark, of Cambridgeport. Mass. who, like most other great improvers of the telescope, is a self-taught artist. It would seem that opticians, like poets, are born, not made. Mr. Clark's first objectglass-es. strange to say, were made for England, but in 1862 he completed one having a clear aptorial refracting telescope at Washington, D. C. at Washington, completed in November. 1873. Mr. Clark is confident of being able to produce an object-glass of 5 feet 6 inches clear aperture and 75hes aperture; 14 ft. 4 1/2 in. focal length Alleghany City13 inches aperture. The disks for Clark's lenses are made by Chance & Co., of Birmingham, England. The crucibles are of clay, and areits total length being 32 feet 6 inches. The rough glass for the object-lens was received by Messrs. Clark in December, 1871, and was ground, polished, and finished in November, 1872. Another year w